1. Field of the Invention
The invention relates to an apparatus for swapping at least one disk-like member, a method for transporting wafers, and a handling line for carrying out the method for transporting wafers.
2. Description of Related Art
Apparatus for accepting and transferring wafers are well known in the art. For instance, robot handlers are commonly used to move materials, e.g. semiconductor wafers, between different stages of a wafer fabrication process. In this regard, robot handlers might be used to move the wafer from a plasma etch station in a cluster tool to a deposition station or from a manufacturing station to a testing station or metrology tool, wherein the wafer is positioned onto a chuck. In this kind of handling system the throughput depends strongly on the time the metrology tool has to wait for material handed over by the robot handler.
A typical transporting or handling scenario for a wafer handling system is the following:                a) the handling system, typically a one-arm-robot-handler gets a new wafer,        b) the handling system moves and loads the wafer onto the transfer position for transferring the wafer for example into the metrology tool,        c) the wafer gets moved into the tool for processing or measuring; after this the wafer gets back to the transfer position or unload position which is typically the same as the load position,        d) the handling system, i.e. the robot handler, picks the wafer and unloads the wafer to the next position,        
The cycle starts from step a)
During the processing of the wafer in the metrology tool the handling system or robot waits or is doing different tasks. But for doing different tasks the handling system has to do motions without wafer. This however is ineffective and forms a bottleneck of the transport system, which limits the throughput.
The problem might be solved by employing a so-called dual-arm or paddle-robot that can handle two wafers at the same time. However, such a handling system has a increased footprint, since the arms increase the sweep radius of the robot, which is caused by the space that is needed horizontally to swap the wafer at the desired station.
Yet, space in a clean room environment, which is commonly needed for wafer production, is a scarce resource. Therefore, an increase in food print of the handling system would raise production costs considerably. Moreover these kind of robots are more complex in handling and their purchase price is high.
Therefore, a solution is needed which on the one side increases the throughput and on the other minimizes the space consumption and the additional footprint, respectively, needed.
These and other disadvantages have lead to the object of the present invention to provide an apparatus as a part of a handling system which avoids to use complex handling systems with a big footprint but nevertheless can increases the throughput considerably.